From: Prashanth K <quic_prashk@xxxxxxxxxxx> [ Upstream commit e5990469943c711cb00bfde6338d2add6c6d0bfe ] When serial console over USB is enabled, gs_console_connect queues gs_console_work, where it acquires the spinlock and queues the usb request, and this request goes to gadget layer. Now consider a situation where gadget layer prints something to dmesg, this will eventually call gs_console_write() which requires cons->lock. And this causes spinlock recursion. Avoid this by excluding usb_ep_queue from the spinlock. spin_lock_irqsave //needs cons->lock gs_console_write . . _printk __warn_printk dev_warn/pr_err . . [USB Gadget Layer] . . usb_ep_queue gs_console_work __gs_console_push // acquires cons->lock process_one_work Signed-off-by: Prashanth K <quic_prashk@xxxxxxxxxxx> Link: https://lore.kernel.org/r/1683638872-6885-1-git-send-email-quic_prashk@xxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- drivers/usb/gadget/function/u_serial.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c index db6fd0238d4b4..2dcd30c96e20d 100644 --- a/drivers/usb/gadget/function/u_serial.c +++ b/drivers/usb/gadget/function/u_serial.c @@ -915,8 +915,11 @@ static void __gs_console_push(struct gs_console *cons) } req->length = size; + + spin_unlock_irq(&cons->lock); if (usb_ep_queue(ep, req, GFP_ATOMIC)) req->length = 0; + spin_lock_irq(&cons->lock); } static void gs_console_work(struct work_struct *work) -- 2.39.2
